1. Field of the Invention
The present invention relates to new crystalline zeolite SSZ-57 and processes employing SSZ-57 as a catalyst.
2. State of the Art
Because of their unique sieving characteristics, as well as their catalytic properties, crystalline molecular sieves and zeolites are especially useful in applications such as hydrocarbon conversion, gas drying and separation. Although many different crystalline molecular sieves have been disclosed, there is a continuing need for new zeolites with desirable properties for gas separation and drying, hydrocarbon and chemical conversions, and other applications. New zeolites may contain novel internal pore architectures, providing enhanced selectivities in these processes.
Crystalline aluminosilicates are usually prepared from aqueous reaction mixtures containing alkali or alkaline earth metal oxides, silica, and alumina. Crystalline borosilicates are usually prepared under similar reaction conditions except that boron is used in place of aluminum. By varying the synthesis conditions and the composition of the reaction mixture, different zeolites can often be formed.
The present invention is directed to a family of crystalline molecular sieves with unique properties, referred to herein as xe2x80x9czeolite SSZ-57xe2x80x9d or simply xe2x80x9cSSZ-57xe2x80x9d. Preferably, SSZ-57 is obtained in its borosilicate form, but the present novel zeolite can be synthesized in the borosilicate, aluminosilicate or all-silicate phase. The term xe2x80x9cborosilicatexe2x80x9d refers to a zeolite containing oxides of both boron and silicon. The term xe2x80x9caluminosilicate refers to a zeolite containing oxides of both aluminum and silicon.
The present invention provides a process for converting hydrocarbons comprising contacting a hydrocarbonaceous feed at hydrocarbon converting conditions with a catalyst comprising the zeolite of this invention. The zeolite may be predominantly in the hydrogen form. It may also be substantially free of acidity.
Further provided by the present invention is a hydrocracking process comprising contacting a hydrocarbon feedstock under hydrocracking conditions with a catalyst comprising the zeolite of this invention, preferably predominantly in the hydrogen form.
This invention also includes a dewaxing process comprising contacting a hydrocarbon feedstock under dewaxing conditions with a catalyst comprising the zeolite of this invention, preferably predominantly in the hydrogen form.
The present invention also includes a process for improving the viscosity index of a dewaxed product of waxy hydrocarbon feeds comprising contacting the waxy hydrocarbon feed under isomerization dewaxing conditions with a catalyst comprising the zeolite of this invention, preferably predominantly in the hydrogen form.
The present invention further includes a process for producing a C20+ lube oil from a C20+ olefin feed comprising isomerizing said olefin feed under isomerization conditions over a catalyst comprising at least one Group VIII metal and the zeolite of this invention. The zeolite may be predominantly in the hydrogen form.
In accordance with this invention, there is also provided a process for catalytically dewaxing a hydrocarbon oil feedstock boiling above about 350 F and containing straight chain and slightly branched chain hydrocarbons comprising contacting said hydrocarbon oil feedstock in the presence of added hydrogen gas at a hydrogen pressure of about 15-3000 psi with a catalyst comprising at least one Group VIII metal and the zeolite of this invention, preferably predominantly in the hydrogen form. The catalyst may be a layered catalyst comprising a first layer comprising at least one Group VIII metal and the zeolite of this invention, and a second layer comprising an aluminosilicate zeolite which is more shape selective than the zeolite of said first layer.
Also included in the present invention is a process for preparing a lubricating oil which comprises hydrocracking in a hydrocracking zone a hydrocarbonaceous feedstock to obtain an effluent comprising a hydrocracked oil, and catalytically dewaxing said effluent comprising hydrocracked oil at a temperature of at least about 400xc2x0 F. and at a pressure of from about 15 psig to about 3000 psig in the presence of added hydrogen gas with a catalyst comprising at least one Group VIII metal and the zeolite of this invention. The zeolite may be predominantly in the hydrogen form.
Further included in this invention is a process for isomerization dewaxing a raffinate comprising contacting said raffinate in the presence of added hydrogen with a catalyst comprising at least one Group VIII metal and the zeolite of this invention. The raffinate may be bright stock, and the zeolite may be predominantly in the hydrogen form.
Also included in this invention is a process for increasing the octane of a hydrocarbon feedstock to produce a product having an increased aromatics content comprising contacting a hydrocarbonaceous feedstock which comprises normal and slightly branched hydrocarbons having a boiling range above about 40xc2x0 C. and less than about 200xc2x0 C., under aromatic conversion conditions with a catalyst comprising the zeolite of this invention made substantially free of acidity by neutralizing said zeolite with a basic metal. Also provided in this invention is such a process wherein the zeolite contains a Group VIII metal component.
Also provided by the present invention is a catalytic cracking process comprising contacting a hydrocarbon feedstock in a reaction zone under catalytic cracking conditions in the absence of added hydrogen with a catalyst comprising the zeolite of this invention, preferably predominantly in the hydrogen form. Also included in this invention is such a catalytic cracking process wherein the catalyst additionally comprises a large pore crystalline cracking component.
This invention further provides an isomerization process for isomerizing C4 to C7 hydrocarbons, comprising contacting a feed having normal and slightly branched C4 to C7 hydrocarbons under isomerizing conditions with a catalyst comprising the zeolite of this invention, preferably predominantly in the hydrogen form. The zeolite may be impregnated with at least one Group VIII metal, preferably platinum. The catalyst may be calcined in a steam/air mixture at an elevated temperature after impregnation of the Group VIII metal.
Also provided by the present invention is a process for alkylating an aromatic hydrocarbon which comprises contacting under alkylation conditions at least a molar excess of an aromatic hydrocarbon with a C2 to C20 olefin under at least partial liquid phase conditions and in the presence of a catalyst comprising the zeolite of this invention, preferably predominantly in the hydrogen form. The olefin may be a C2 to C4 olefin, and the aromatic hydrocarbon and olefin may be present in a molar ratio of about 4:1 to about 20:1, respectively. The aromatic hydrocarbon may be selected from the group consisting of benzene, toluene, ethyl benzene, xylene, naphthalene, dimethylnaphthalene, naphthalene derivatives or mixtures thereof.
Further provided in accordance with this invention is a process for transalkylating an aromatic hydrocarbon which comprises contacting under transalkylating conditions an aromatic hydrocarbon with a polyalkyl aromatic hydrocarbon under at least partial liquid phase conditions and in the presence of a catalyst comprising the zeolite of this invention, preferably predominantly in the hydrogen form. The aromatic hydrocarbon and the polyalkyl aromatic hydrocarbon may be present in a molar ratio of from about 1:1 to about 25:1, respectively.
The aromatic hydrocarbon may be selected from the group consisting of benzene, toluene, ethylbenzene, xylene, or mixtures thereof, and the polyalkyl aromatic hydrocarbon may be a dialkylbenzene.
Further provided by this invention is a process to convert paraffins to aromatics which comprises contacting paraffins under conditions which cause paraffins to convert to aromatics with a catalyst comprising the zeolite of this invention, said catalyst comprising gallium, zinc, or a compound of gallium or zinc.
In accordance with this invention, there is also provided a process for isomerizing olefins comprising contacting said olefin under conditions which cause isomerization of the olefin with a catalyst comprising the zeolite of this invention.
Further provided in accordance with this invention is a process for isomerizing an isomerization feed comprising an aromatic C8 stream of xylene isomers or mixtures of xylene isomers and ethylbenzene, wherein a more nearly equilibrium ratio of ortho-, meta- and para-xylenes is obtained, said process comprising contacting said feed under isomerization conditions with a catalyst comprising the zeolite of this invention.
The present invention further provides a process for oligomerizing olefins comprising contacting an olefin feed under oligomerization conditions with a catalyst comprising the zeolite of this invention.
This invention also provides a process for converting lower alcohols and other oxygenated hydrocarbons comprising contacting said lower alcohol or other oxygenated hydrocarbon with a catalyst comprising the zeolite of this invention under conditions to produce liquid products.
Further provided in accordance with the present invention is a process for the production of higher molecular weight hydrocarbons from lower molecular weight hydrocarbons comprising the steps of:
(a) introducing into a reaction zone a lower molecular weight hydrocarbon-containing gas and contacting said gas in said zone under C2+ hydrocarbon synthesis conditions with the catalyst and a metal or metal compound capable of converting the lower molecular weight hydrocarbon to a higher molecular weight hydrocarbon; and
(b) withdrawing from said reaction zone a higher molecular weight hydrocarbon-containing stream.
The present invention comprises a family of crystalline zeolites designated herein xe2x80x9czeolite SSZ-57xe2x80x9d or simply xe2x80x9cSSZ-57xe2x80x9d.
In preparing SSZ-57 zeolites, a N-cyclohexyl-N-butylpyrrolidinium ammonium cation, N-propyl-N-cycloheptylpyrrolidinium cation or N-butyl-N-cyclooctylpyrrolidinium is used as a crystallization template. In general, SSZ-57 is prepared by contacting an active source of an oxide selected from silicon oxide alone or silicon oxide, germanium oxide and mixtures thereof and boron oxide, aluminum oxide, gallium oxide, indium oxide, titanium oxide, iron oxide, vanadium oxide or a mixture thereof with the templating agent.
SSZ-57 is prepared from a reaction mixture having the composition shown in Table A below.
wherein Y is silicon, germanium or a mixture thereof; W is boron, aluminum, gallium, indium, titanium, iron, vanadium or a mixture thereof; M is an alkali metal cation, alkaline earth metal cation or mixtures thereof; n is the valence of M (i.e., 1 or 2); and a is 1 or 2 and b is 2 when a is 1 (i.e., W is tetravalent) or b is 3 when a is 2 (i.e., W is trivalent). When YO2/WaOb is xe2x88x9d and Y is silicon, the SSZ-57 will be all-silica SSZ-57.
In practice, SSZ-57 is prepared by a process comprising:
(a) preparing an aqueous solution containing sources of at least one oxide capable of forming a crystalline molecular sieve and the N-butyl-N-cyclohexylpyrrolidinium cation, N-propyl-N-cycloheptylpyrrolidinium cation or N-butyl-N-cyclooctylpyrrolidinium in the presence of an anionic counterion which is not detrimental to the formation of SSZ-57;
(b) maintaining the aqueous solution under conditions sufficient to form crystals of SSZ-57; and
(c) recovering the crystals of SSZ-57.
Accordingly, SSZ-57 may comprise the crystalline material and the templating agent in combination with metallic and non-metallic oxides bonded in tetrahedral coordination through shared oxygen atoms to form a cross-linked three dimensional crystal structure. The metallic and non-metallic oxides comprise an oxide selected from silicon oxide, germanium oxide and mixtures thereof and boron oxide, aluminum oxide, gallium oxide, indium oxide, titanium oxide, iron oxide, vanadium oxide or a mixture thereof.
Typical sources of silicon oxide include silicates, silica hydrogel, silicic acid, fumed silica, colloidal silica, tetra-alkyl orthosilicates, and silica hydroxides. Boron, as well as aluminum, gallium, germanium, titanium, indium, iron and vanadium can be added in forms corresponding to their silicon counterparts.
A source zeolite reagent may provide a source of boron. In most cases, the source zeolite also provides a source of silica. The source zeolite in its dealuminated or deboronated form may also be used as a source of silica, with additional silicon added using, for example, the conventional sources listed above. Use of a source zeolite reagent as a source of alumina for the present process is more completely described in U.S. Pat. No. 5,225,179, issued Jul. 6, 1993 to Nakagawa entitled xe2x80x9cMethod of Making Molecular Sievesxe2x80x9d, the disclosure of which is incorporated herein by reference.
Typically, an alkali metal hydroxide and/or an alkaline earth metal hydroxide, such as the hydroxide of sodium, potassium, lithium, cesium, rubidium, calcium, and magnesium, is used in the reaction mixture; however, this component can be omitted so long as the equivalent basicity is maintained. The templating agent may be used to provide hydroxide ion. Thus, it may be beneficial to ion exchange, for example, the halide for hydroxide ion, thereby reducing or eliminating the alkali metal hydroxide quantity required. The alkali metal cation or alkaline earth cation may be part of the as-synthesized crystalline oxide material, in order to balance valence electron charges therein.
The reaction mixture is maintained at an elevated temperature until the crystals of the SSZ-57 zeolite are formed. The hydrothermal crystallization is usually conducted under autogenous pressure, at a temperature between 100xc2x0 C. and 200xc2x0 C., preferably between 135xc2x0 C. and 160xc2x0 C. The crystallization period is typically greater than 1 day and preferably from about 3 days to about 20 days.
Preferably, the zeolite is prepared using mild stirring or agitation.
During the hydrothermal crystallization step, the SSZ-57 crystals can be allowed to nucleate spontaneously from the reaction mixture. The use of SSZ-57 crystals as seed material can be advantageous in decreasing the time necessary for complete crystallization to occur. In addition, seeding can lead to an increased purity of the product obtained by promoting the nucleation and/or formation of SSZ-57 over any undesired phases. When used as seeds, SSZ-57 crystals are added in an amount between 0.1 and 10% of the weight of silica used in the reaction mixture.
Once the zeolite crystals have formed, the solid product is separated from the reaction mixture by standard mechanical separation techniques such as filtration. The crystals are water-washed and then dried, e.g., at 90xc2x0 C. to 150xc2x0 C. for from 8 to 24 hours, to obtain the as-synthesized SSZ-57 zeolite crystals. The drying step can be performed at atmospheric pressure or under vacuum.
SSZ-57, as prepared, has a mole ratio of an oxide selected from silicon oxide, germanium oxide and mixtures thereof to boron oxide or a combination of boron oxide and aluminum oxide, gallium oxide, indium oxide, titanium oxide or a mixture thereof greater than about 20; and has the X-ray diffraction lines of Table I below. SSZ-57 further has a composition, as-synthesized and in the anhydrous state, in terms of mole ratios, shown in Table B below.
where Y, W, M, n and Q are as defined above and c is 1 or 2; d is 2 when c is 1 (i.e., W is tetravalent) or d is 3 or 5 when c is 2 (i.e., d is 3 when W is trivalent or 5 when W is pentavalent). When YO2/WcOd is xe2x88x9d and Y is silicon, the SSZ-57 will be all-silica SSZ-57.
SSZ-57 can be made essentially aluminum free, i.e., having a silica to alumina mole ratio approaching ∞. A method of increasing the mole ratio of silica to alumina is by using standard acid leaching or chelating treatments. However, essentially aluminum-free SSZ-57 can be synthesized directly using essentially aluminum-free silicon and boron sources. SSZ-57 is generally prepared directly as a borosilicate. Lower silica to alumina ratios may also be obtained by using methods which insert aluminum into the crystalline framework. For example, aluminum insertion may occur by thermal treatment of the zeolite in combination with an alumina binder or dissolved source of alumina. Such procedures are described in U.S. Pat. No. 4,559,315, issued on Dec. 17, 1985 to Chang et al.
It is believed that SSZ-57 is comprised of a new framework structure or topology which is characterized by its X-ray diffraction pattern. SSZ-57 zeolites, as-synthesized, have a crystalline structure whose X-ray powder diffraction pattern exhibit the characteristic lines shown in Table 1 and is thereby distinguished from other zeolites.
The complete X-ray diffraction pattern of a boron SSZ-57 zeolite is shown in Table 2 below:
After calcination, the SSZ-57 zeolites have a crystalline structure whose X-ray powder diffraction pattern include the characteristic lines shown in Table 3:
The complete X-ray diffraction pattern for an SSZ-57 calcined zeolite is shown in Table 4:
The X-ray powder diffraction patterns were determined by standard techniques. The radiation was the K-alpha/doublet of copper. The peak heights and the positions, as a function of 2 Theta where Theta is the Bragg angle, were read from the relative intensities of the peaks, and d, the interplanar spacing in Angstroms corresponding to the recorded lines, can be calculated.
The variation in the scattering angle (two theta) measurements, due to instrument error and to differences between individual samples, is estimated at xc2x10.15 degrees.
The X-ray diffraction pattern of Table 1 is representative of xe2x80x9cas-synthesizedxe2x80x9d or xe2x80x9cas-madexe2x80x9d SSZ-57 zeolites. Minor variations in the diffraction pattern can result from variations in the silica-to-boron or silica-to-alumina mole ratio of the particular sample due to changes in lattice constants. In addition, sufficiently small crystals will affect the shape and intensity of peaks, leading to significant peak broadening.
Representative peaks from the X-ray diffraction pattern of calcined SSZ-57 are shown in Table 3. Calcination can also result in changes in the intensities of the peaks as compared to patterns of the xe2x80x9cas-madexe2x80x9d material, as well as minor shifts in the diffraction pattern. The zeolite produced by exchanging the metal or other cations present in the zeolite with various other cations (such as H+ or NH4+) yields essentially the same diffraction pattern, although again, there may be minor shifts in the interplanar spacing and variations in the relative intensities of the peaks. Notwithstanding these minor perturbations, the basic crystal lattice remains unchanged by these treatments.
Crystalline SSZ-57 can be used as-synthesized, but preferably will be thermally treated (calcined). Usually, it is desirable to remove the alkali metal cation by ion exchange and replace it with hydrogen, ammonium, or any desired metal ion. The zeolite can be leached with chelating agents, e.g., EDTA or dilute acid solutions, to increase the silica to alumina mole ratio. The zeolite can also be steamed; steaming helps stabilize the crystalline lattice to attack from acids.
The zeolite can be used in intimate combination with hydrogenating components, such as tungsten, vanadium molybdenum, rhenium, nickel cobalt, chromium, manganese, or a noble metal, such as palladium or platinum, for those applications in which a hydrogenation-dehydrogenation function is desired.
Metals may also be introduced into the zeolite by replacing some of the cations in the zeolite with metal cations via standard ion exchange techniques (see, for example, U.S. Pat. No. 3,140,249 issued Jul. 7, 1964 to Plank et al.; U.S. Pat. No. 3,140,251 issued Jul. 7, 1964 to Plank et al.; and U.S. Pat. No. 3,140,253 issued Jul. 7, 1964 to Plank et al.). Typical replacing cations can include metal cations, e.g., rare earth, Group IA, Group IIA and Group VIII metals, as well as their mixtures. Of the replacing metallic cations, cations of metals such as rare earth, Mn, Ca, Mg, Zn, Cd, Pt, Pd, Ni, Co, Ti, Al, Sn, and Fe are particularly preferred.
The hydrogen, ammonium, and metal components can be ion-exchanged into the SSZ-57. The zeolite can also be impregnated with the metals, or the metals can be physically and intimately admixed with the zeolite using standard methods known to the art.
Typical ion-exchange techniques involve contacting the synthetic zeolite with a solution containing a salt of the desired replacing cation or cations. Although a wide variety of salts can be employed, chlorides and other halides, acetates, nitrates, and sulfates are particularly preferred. The zeolite is usually calcined prior to the ion-exchange procedure to remove the organic matter present in the channels and on the surface, since this results in a more effective ion exchange. Representative ion exchange techniques are disclosed in a wide variety of patents including U.S. Pat. No. 3,140,249 issued on Jul. 7, 1964 to Plank et al.; U.S. Pat. No. 3,140,251 issued on Jul. 7, 1964 to Plank et al.; and U.S. Pat. No. 3,140,253 issued on Jul. 7, 1964 to Plank et al.
Following contact with the salt solution of the desired replacing cation, the zeolite is typically washed with water and dried at temperatures ranging from 65xc2x0 C. to about 200xc2x0 C. After washing, the zeolite can be calcined in air or inert gas at temperatures ranging from about 200xc2x0 C. to about 800xc2x0 C. for periods of time ranging from 1 to 48 hours, or more, to produce a catalytically active product especially useful in hydrocarbon conversion processes.
Regardless of the cations present in the synthesized form of SSZ-57, the spatial arrangement of the atoms which form the basic crystal lattice of the zeolite remains essentially unchanged.
SSZ-57 can be formed into a wide variety of physical shapes. Generally speaking, the zeolite can be in the form of a powder, a granule, or a molded product, such as extrudate having a particle size sufficient to pass through a 2-mesh (Tyler) screen and be retained on a 400-mesh (Tyler) screen. In cases where the catalyst is molded, such as by extrusion with an organic binder, the aluminosilicate can be extruded before drying, or dried or partially dried and then extruded.
SSZ-57 can be composited with other materials resistant to the temperatures and other conditions employed in organic conversion processes. Such matrix materials include active and inactive materials and synthetic or naturally occurring zeolites as well as inorganic materials such as clays, silica and metal oxides. Examples of such materials and the manner in which they can be used are disclosed in U.S. Pat. No. 4,910,006, issued May 20, 1990 to Zones et al., and U.S. Pat. No. 5,316,753, issued May 31, 1994 to Nakagawa, both of which are incorporated by reference herein in their entirety.
SSZ-57 zeolites are useful in hydrocarbon conversion reactions. Hydrocarbon conversion reactions are chemical and catalytic processes in which carbon containing compounds are changed to different carbon containing compounds. Examples of hydrocarbon conversion reactions in which SSZ-57 are expected to be useful include hydrocracking, dewaxing, catalytic cracking and olefin and aromatics formation reactions. The catalysts are also expected to be useful in other petroleum refining and hydrocarbon conversion reactions such as isomerizing n-paraffins and naphthenes, polymerizing and oligomerizing olefinic or acetylenic compounds such as isobutylene and butene-1, reforming, isomerizing polyalkyl substituted aromatics (e.g., m-xylene), and disproportionating aromatics (e.g., toluene) to provide mixtures of benzene, xylenes and higher methylbenzenes and oxidation reactions. Also included are rearrangement reactions to make various naphthalene derivatives, and forming higher molecular weight hydrocarbons from lower molecular weight hydrocarbons (e.g., methane upgrading). The SSZ-57 catalysts may have high selectivity, and under hydrocarbon conversion conditions can provide a high percentage of desired products relative to total products.
SSZ-57 zeolites can be used in processing hydrocarbonaceous feedstocks. Hydrocarbonaceous feedstocks contain carbon compounds and can be from many different sources, such as virgin petroleum fractions, recycle petroleum fractions, shale oil, liquefied coal, tar sand oil, synthetic paraffins from NAO, recycled plastic feedstocks and, in general, can be any carbon containing feedstock susceptible to zeolitic catalytic reactions. Depending on the type of processing the hydrocarbonaceous feed is to undergo, the feed can contain metal or be free of metals; it can also have high or low nitrogen or sulfur impurities. It can be appreciated, however, that in general processing will be more efficient (and the catalyst more active) the lower the metal, nitrogen, and sulfur content of the feedstock.
The conversion of hydrocarbonaceous feeds can take place in any convenient mode, for example, in fluidized bed, moving bed, or fixed bed reactors depending on the types of process desired. The formulation of the catalyst particles will vary depending on the conversion process and method of operation.
Other reactions which can be performed using the catalyst of this invention containing a metal, e.g., a Group VIII metal such as platinum, include hydrogenation-dehydrogenation reactions, denitrogenation and desulfurization reactions.
The following Table III indicates typical reaction conditions which may be employed when using catalysts comprising SSZ-57 in the hydrocarbon conversion reactions of this invention. Preferred conditions are indicated in parentheses.
Other reaction conditions and parameters are provided below.
Using a catalyst which comprises SSZ-57, preferably predominantly in the hydrogen form, and a hydrogenation promoter, heavy petroleum residual feedstocks, cyclic stocks and other hydrocrackate charge stocks can be hydrocracked using the process conditions and catalyst components disclosed in the aforementioned U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753.
The hydrocracking catalysts contain an effective amount of at least one hydrogenation component of the type commonly employed in hydrocracking catalysts. The hydrogenation component is generally selected from the group of hydrogenation catalysts consisting of one or more metals of Group VIB and Group VIII, including the salts, complexes and solutions containing such. The hydrogenation catalyst is preferably selected from the group of metals, salts and complexes thereof of the group consisting of at least one of platinum, palladium, rhodium, iridium, ruthenium and mixtures thereof or the group consisting of at least one of nickel, molybdenum, cobalt, tungsten, titanium, chromium and mixtures thereof. Reference to the catalytically active metal or metals is intended to encompass such metal or metals in the elemental state or in some form such as an oxide, sulfide, halide, carboxylate and the like. The hydrogenation catalyst is present in an effective amount to provide the hydrogenation function of the hydrocracking catalyst, and preferably in the range of from 0.05 to 25% by weight.
SSZ-57, preferably predominantly in the hydrogen form, can be used to dewax hydrocarbonaceous feeds by selectively removing straight chain paraffins. Typically, the viscosity index of the dewaxed product is improved (compared to the waxy feed) when the waxy feed is contacted with SSZ-57 under isomerization dewaxing conditions.
The catalytic dewaxing conditions are dependent in large measure on the feed used and upon the desired pour point. Hydrogen is preferably present in the reaction zone during the catalytic dewaxing process. The hydrogen to feed ratio is typically between about 500 and about 30,000 SCF/bbl (standard cubic feet per barrel), preferably about 1000 to about 20,000 SCF/bbl. Generally, hydrogen will be separated from the product and recycled to the reaction zone. Typical feedstocks include light gas oil, heavy gas oils and reduced crudes boiling above about 350xc2x0 F.
A typical dewaxing process is the catalytic dewaxing of a hydrocarbon oil feedstock boiling above about 350xc2x0 F. and containing straight chain and slightly branched chain hydrocarbons by contacting the hydrocarbon oil feedstock in the presence of added hydrogen gas at a hydrogen pressure of about 15-3000 psi with a catalyst comprising SSZ-57 and at least one Group VIII metal.
The SSZ-57 hydrodewaxing catalyst may optionally contain a hydrogenation component of the type commonly employed in dewaxing catalysts. See the aforementioned U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753 for examples of these hydrogenation components.
The hydrogenation component is present in an effective amount to provide an effective hydrodewaxing and hydroisomerization catalyst preferably in the range of from about 0.05 to 5% by weight. The catalyst may be run in such a mode to increase isodewaxing at the expense of cracking reactions.
The feed may be hydrocracked, followed by dewaxing. This type of two-stage process and typical hydrocracking conditions are described in U.S. Pat. No. 4,921,594, issued May 1, 1990 to Miller, which is incorporated herein by reference in its entirety.
SSZ-57 may also be utilized as a dewaxing catalyst in the form of a layered catalyst. That is, the catalyst comprises a first layer comprising zeolite SSZ-57 and at least one Group VIII metal, and a second layer comprising an aluminosilicate zeolite which is more shape selective than zeolite SSZ-56. The use of layered catalysts is disclosed in U.S. Pat. No. 5,149,421, issued Sep. 22, 1992 to Miller, which is incorporated by reference herein in its entirety. The layering may also include a bed of SSZ-57 layered with a non-zeolitic component designed for either hydrocracking or hydrofinishing.
SSZ-57 may also be used to dewax raffinates, including bright stock, under conditions such as those disclosed in U. S. Pat. No. 4,181,598, issued Jan. 1, 1980 to Gillespie et al., which is incorporated by reference herein in its entirety.
It is often desirable to use mild hydrogenation (sometimes referred to as hydrofinishing) to produce more stable dewaxed products. The hydrofinishing step can be performed either before or after the dewaxing step, and preferably after. Hydrofinishing is typically conducted at temperatures ranging from about 190xc2x0 C. to about 340xc2x0 C. at pressures from about 400 psig to about 3000 psig at space velocities (LHSV) between about 0.1 and 20 and a hydrogen recycle rate of about 400 to 1500 SCF/bbl. The hydrogenation catalyst employed must be active enough not only to hydrogenate the olefins, diolefins and color bodies which may be present, but also to reduce the aromatic content. Suitable hydrogenation catalyst are disclosed in U. S. Pat. No. 4,921,594, issued May 1, 1990 to Miller, which is incorporated by reference herein in its entirety. The hydrofinishing step is beneficial in preparing an acceptably stable product (e.g., a lubricating oil) since dewaxed products prepared from hydrocracked stocks tend to be unstable to air and light and tend to form sludges spontaneously and quickly.
Lube oil may be prepared using SSZ-57. For example, a C20+ lube oil may be made by isomerizing a C20+ olefin feed over a catalyst comprising SSZ-57 in the hydrogen form and at least one Group VIII metal. Alternatively, the lubricating oil may be made by hydrocracking in a hydrocracking zone a hydrocarbonaceous feedstock to obtain an effluent comprising a hydrocracked oil, and catalytically dewaxing the effluent at a temperature of at least about 400xc2x0 F. and at a pressure of from about 15 psig to about 3000 psig in the presence of added hydrogen gas with a catalyst comprising SSZ-57 in the hydrogen form and at least one Group VIII metal.
SSZ-57 can be used to convert light straight run naphthas and similar mixtures to highly aromatic mixtures. Thus, normal and slightly branched chained hydrocarbons, preferably having a boiling range above about 40xc2x0 C. and less than about 200xc2x0 C., can be converted to products having a substantial higher octane aromatics content by contacting the hydrocarbon feed with a catalyst comprising SSZ-57. It is also possible to convert heavier feeds into BTX or naphthalene derivatives of value using a catalyst comprising SSZ-57.
The conversion catalyst preferably contains a Group VIII metal compound to have sufficient activity for commercial use. By Group VIII metal compound as used herein is meant the metal itself or a compound thereof. The Group VIII noble metals and their compounds, platinum, palladium, and iridium, or combinations thereof can be used. Rhenium or tin or a mixture thereof may also be used in conjunction with the Group VIII metal compound and preferably a noble metal compound. The most preferred metal is platinum. The amount of Group VIII metal present in the conversion catalyst should be within the normal range of use in reforming catalysts, from about 0.05 to 2.0 weight percent, preferably 0.2 to 0.8 weight percent.
It is critical to the selective production of aromatics in useful quantities that the conversion catalyst be substantially free of acidity, for example, by neutralizing the zeolite with a basic metal, e.g., alkali metal, compound. Methods for rendering the catalyst free of acidity are known in the art. See the aforementioned U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753 for a description of such methods.
The preferred alkali metals are sodium, potassium, rubidium and cesium. The zeolite itself can be substantially free of acidity only at very high silica:alumina mole ratios.
Hydrocarbon cracking stocks can be catalytically cracked in the absence of hydrogen using SSZ-57, preferably predominantly in the hydrogen form.
When SSZ-57 is used as a catalytic cracking catalyst in the absence of hydrogen, the catalyst may be employed in conjunction with traditional cracking catalysts, e.g., any aluminosilicate heretofore employed as a component in cracking catalysts. Typically, these are large pore, crystalline aluminosilicates. Examples of these traditional cracking catalysts are disclosed in the aforementioned U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753. When a traditional cracking catalyst (TC) component is employed, the relative weight ratio of the TC to the SSZ-57 is generally between about 1:10 and about 500:1, desirably between about 1:10 and about 200:1, preferably between about 1:2 and about 50:1, and most preferably is between about 1:1 and about 20:1. The novel zeolite and/or the traditional cracking component may be further ion exchanged with rare earth ions to modify selectivity.
The cracking catalysts are typically employed with an inorganic oxide matrix component. See the aforementioned U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753 for examples of such matrix components.
The present catalyst is highly active and highly selective for isomerizing C4 to C7 hydrocarbons. The activity means that the catalyst can operate at relatively low temperature which thermodynamically favors highly branched paraffins. Consequently, the catalyst can produce a high octane product. The high selectivity means that a relatively high liquid yield can be achieved when the catalyst is run at a high octane.
The present process comprises contacting the isomerization catalyst, i.e., a catalyst comprising SSZ-57 in the hydrogen form, with a hydrocarbon feed under isomerization conditions. The feed is preferably a light straight run fraction, boiling within the range of 30xc2x0 F. to 250xc2x0 F. and preferably from 60xc2x0 F. to 200xc2x0 F. Preferably, the hydrocarbon feed for the process comprises a substantial amount of C4 to C7 normal and slightly branched low octane hydrocarbons, more preferably C5 and C6 hydrocarbons.
It is preferable to carry out the isomerization reaction in the presence of hydrogen. Preferably, hydrogen is added to give a hydrogen to hydrocarbon ratio (H2/HC) of between 0.5 and 10 H2/HC, more preferably between 1 and 8 H2/HC. See the aforementioned U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753 for a further discussion of isomerization process conditions.
A low sulfur feed is especially preferred in the present process. The feed preferably contains less than 10 ppm, more preferably less than 1 ppm, and most preferably less than 0.1 ppm sulfur. In the case of a feed which is not already low in sulfur, acceptable levels can be reached by hydrogenating the feed in a presaturation zone with a hydrogenating catalyst which is resistant to sulfur poisoning. See the aforementioned U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753 for a further discussion of this hydrodesulfurization process.
It is preferable to limit the nitrogen level and the water content of the feed. Catalysts and processes which are suitable for these purposes are known to those skilled in the art.
After a period of operation, the catalyst can become deactivated by sulfur or coke. See the aforementioned U.S. Pat. No. 4,910,006 and U.S. Pat. No. 5,316,753 for a further discussion of methods of removing this sulfur and coke, and of regenerating the catalyst.
The conversion catalyst preferably contains a Group VIII metal compound to have sufficient activity for commercial use. By Group VIII metal compound as used herein is meant the metal itself or a compound thereof. The Group VIII noble metals and their compounds, platinum, palladium, and iridium, or combinations thereof can be used. Rhenium and tin may also be used in conjunction with the noble metal. The most preferred metal is platinum. The amount of Group VIII metal present in the conversion catalyst should be within the normal range of use in isomerizing catalysts, from about 0.05 to 2.0 weight percent, preferably 0.2 to 0.8 weight percent.
SSZ-57 can be used in a process for the alkylation or transalkylation of an aromatic hydrocarbon. The process comprises contacting the aromatic hydrocarbon with a C2 to C16 olefin alkylating agent or a polyalkyl aromatic hydrocarbon transalkylating agent, under at least partial liquid phase conditions, and in the presence of a catalyst comprising SSZ-57.
SSZ-57 can also be used for removing benzene from gasoline by alkylating the benzene as described above and removing the alkylated product from the gasoline.
For high catalytic activity, the SSZ-57 zeolite should be predominantly in its hydrogen ion form. It is preferred that, after calcination, at least 80% of the cation sites are occupied by hydrogen ions and/or rare earth ions.
Examples of suitable aromatic hydrocarbon feedstocks which may be alkylated or transalkylated by the process of the invention include aromatic compounds such as benzene, toluene and xylene. The preferred aromatic hydrocarbon is benzene. There may be occasions where naphthalene or naphthalene derivatives such as dimethylnaphthalene may be desirable. Mixtures of aromatic hydrocarbons may also be employed.
Suitable olefins for the alkylation of the aromatic hydrocarbon are those containing 2 to 20 carbon atoms, preferably 2 to 4 carbon atoms, such as ethylene, propylene, butene-1, trans-butene-2 and cis-butene-2, or mixtures thereof. There may be instances where pentenes are desirable. The preferred olefins are ethylene and propylene. Longer chain alpha olefins may be used as well.
When transalkylation is desired, the transalkylating agent is a polyalkyl aromatic hydrocarbon containing two or more alkyl groups that each may have from 2 to about 4 carbon atoms. For example, suitable polyalkyl aromatic hydrocarbons include di-, tri- and tetra-alkyl aromatic hydrocarbons, such as diethylbenzene, triethylbenzene, diethylmethylbenzene (diethyltoluene), di-isopropylbenzene, di-isopropyltoluene, dibutylbenzene, and the like. Preferred polyalkyl aromatic hydrocarbons are the dialkyl benzenes. A particularly preferred polyalkyl aromatic hydrocarbon is di-isopropylbenzene.
When alkylation is the process conducted, reaction conditions are as follows. The aromatic hydrocarbon feed should be present in stoichiometric excess. It is preferred that molar ratio of aromatics to olefins be greater than four-to-one to prevent rapid catalyst fouling. The reaction temperature may range from 100xc2x0 F. to 600xc2x0 F., preferably 250xc2x0 F. to 450xc2x0 F. The reaction pressure should be sufficient to maintain at least a partial liquid phase in order to retard catalyst fouling. This is typically 50 psig to 1000 psig depending on the feedstock and reaction temperature. Contact time may range from 10 seconds to 10 hours, but is usually from 5 minutes to an hour. The weight hourly space velocity (WHSV), in terms of grams (pounds) of aromatic hydrocarbon and olefin per gram (pound) of catalyst per hour, is generally within the range of about 0.5 to 50.
When transalkylation is the process conducted, the molar ratio of aromatic hydrocarbon will generally range from about 1:1 to 25:1, and preferably from about 2:1 to 20:1. The reaction temperature may range from about 100xc2x0 F. to 600xc2x0 F., but it is preferably about 250xc2x0 F. to 450xc2x0 F. The reaction pressure should be sufficient to maintain at least a partial liquid phase, typically in the range of about 50 psig to 1000 psig, preferably 300 psig to 600 psig. The weight hourly space velocity will range from about 0.1 to 10. U.S. Pat. No. 5,082,990 issued on Jan. 21, 1992 to Hsieh et al. describes such processes and is incorporated herein by reference.
SSZ-57 can be used to convert light gas C2-C6 paraffins to higher molecular weight hydrocarbons including aromatic compounds. Preferably, the zeolite will contain a catalyst metal or metal oxide wherein said metal is selected from the group consisting of Groups IB, IIB, VIII and IIIA of the Periodic Table. Preferably, the metal is gallium, niobium, indium or zinc in the range of from about 0.05 to 5% by weight.
SSZ-57 may also be useful in a process for isomerizing one or more xylene isomers in a C8 aromatic feed to obtain ortho-, meta-, and para-xylene in a ratio approaching the equilibrium value. In particular, xylene isomerization is used in conjunction with a separate process to manufacture para-xylene. For example, a portion of the para-xylene in a mixed C8 aromatics stream may be recovered by crystallization and centrifugation. The mother liquor from the crystallizer is then reacted under xylene isomerization conditions to restore ortho-, meta- and para-xylenes to a near equilibrium ratio. At the same time, part of the ethylbenzene in the mother liquor is converted to xylenes or to products which are easily separated by filtration. The isomerate is blended with fresh feed and the combined stream is distilled to remove heavy and light by-products. The resultant C8 aromatics stream is then sent to the crystallizer to repeat the cycle.
Optionally, isomerization in the vapor phase is conducted in the presence of 3.0 to 30.0 moles of hydrogen per mole of alkylbenzene (e.g., ethylbenzene). If hydrogen is used, the catalyst should comprise about 0.1 to 2.0 wt. % of a hydrogenation/dehydrogenation component selected from Group VIII (of the Periodic Table) metal component, especially platinum or nickel. By Group VIII metal component is meant the metals and their compounds such as oxides and sulfides.
Optionally, the isomerization feed may contain 10 to 90 wt. % of a diluent such as toluene, trimethylbenzene, naphthenes or paraffins.
It is expected that SSZ-57 can also be used to oligomerize straight and branched chain olefins having from about 2 to 21 carbon atoms and preferably 2-5 carbon atoms. The oligomers which are the products of the process are medium to heavy olefins which are useful for both fuels, i.e., gasoline or a gasoline blending stock and chemicals.
The oligomerization process comprises contacting the olefin feedstock in the gaseous or liquid phase with a catalyst comprising SSZ-57.
The zeolite can have the original cations associated therewith replaced by a wide variety of other cations according to techniques well known in the art. Typical cations would include hydrogen, ammonium and metal cations including mixtures of the same. Of the replacing metallic cations, particular preference is given to cations of metals such as rare earth metals, manganese, calcium, as well as metals of Group II of the Periodic Table, e.g., zinc, and Group VIII of the Periodic Table, e.g., nickel. One of the prime requisites is that the zeolite have a fairly low aromatization activity, i.e., in which the amount of aromatics produced is not more than about 20% by weight. This is accomplished by using a zeolite with controlled acid activity [alpha value] of from about 0.1 to about 120, preferably from about 0.1 to about 100, as measured by its ability to crack n-hexane.
Alpha values are defined by a standard test known in the art, e.g., as shown in U.S. Pat. No. 3,960,978 issued on Jun. 1, 1976 to Givens et al. which is incorporated totally herein by reference. If required, such zeolites may be obtained by steaming, by use in a conversion process or by any other method which may occur to one skilled in this art.
SSZ-57 can be used to condense lower aliphatic alcohols having 1 to 10 carbon atoms to a gasoline boiling point hydrocarbon product comprising mixed aliphatic and aromatic hydrocarbon. The process disclosed in U.S. Pat. No. 3,894,107, issued Jul. 8, 1975 to Butter et al., describes the process conditions used in this process, which patent is incorporated totally herein by reference.
The catalyst may be in the hydrogen form or may be base exchanged or impregnated to contain ammonium or a metal cation complement, preferably in the range of from about 0.05 to 5% by weight. The metal cations that may be present include any of the metals of the Groups I through VIII of the Periodic Table. However, in the case of Group IA metals, the cation content should in no case be so large as to effectively inactivate the catalyst, nor should the exchange be such as to eliminate all acidity. There may be other processes involving treatment of oxygenated substrates where a basic catalyst is desired.
Higher molecular weight hydrocarbons can be formed from lower molecular weight hydrocarbons by contacting the lower molecular weight hydrocarbon with a catalyst comprising SSZ-60 and a metal or metal compound capable of converting the lower molecular weight hydrocarbon to a higher molecular weight hydrocarbon. Examples of such reactions include the conversion of methane to C2+ hydrocarbons such as ethylene or benzene or both. Examples of useful metals and metal compounds include lanthanide and or actinide metals or metal compounds.
These reactions, the metals or metal compounds employed and the conditions under which they can be run are disclosed in U.S. Pat. No. 4,734,537, issued Mar. 29, 1988 to Devries et al.; U.S. Pat. No. 4,939,311, issued Jul. 3, 1990 to Washecheck et al.; U.S. Pat. No. 4,962,261, issued Oct. 9, 1990 to Abrevaya et al.; U.S. Pat. No. 5,095,161, issued Mar. 10, 1992 to Abrevaya et al.; U.S. Pat. No. 5,105,044, issued Apr. 14, 1992 to Han et al.; U.S. Pat. No. 5,105,046, issued Apr. 14, 1992 to Washecheck; U.S. Pat. No. 5,238,898, issued Aug. 24, 1993 to Han et al.; U.S. Pat. No. 5,321,185, issued Jun. 14, 1994 to van der Vaart; and U.S. Pat. No. 5,336,825, issued Aug. 9, 1994 to Choudhary et al., each of which is incorporated herein by reference in its entirety.